New sharps are supplied with a protective cap or sheath to protect the user from accidental injury. This cap is removed prior to use and replaced afterwards to avoid danger. The used instrument may be contaminated with infectious material after use and this provides an even more compelling reason to recap the disposable sharp. However, it is the act of recapping that most often causes accidental pricks, injury, and possible infections.
For ease of description, this art and this invention are described in the context of use with syringes which are the most common and widely used disposable sharps. The prior art recognizes numerous kinds of protective caps, covers, and sheaths for syringes. For example, Hollister U.S. Pat. No. 4,982,842 discloses a syringe with a slotted cover for the needle that hinges on the side of the syringe by means of a thin plastic living hinge. After use, the cover is in a convenient position to be rotated to a needle-enclosing configuration. However, the user must grasp the cover with his fingers and move it toward the needle. This is dangerous because any movement of the fingers in close proximity to the needle point inevitably invites a mistake and an injury. Millions of needles are used and accidents will happen eventually. The Hollister patent itself references many other prior art patents relevant to this field.
Another class of prior art sheaths uses two piece clamshell arrangements that close about the needle from both sides, typified by Norelli U.S. Pat. Nos. 4,820,277 and 4,909,792, Cole U.S. Pat. No. 4,944,731, and Landis U.S. Pat. No. 4,664,259. These too are manually operable, requiring the user to squeeze the cover halves toward the needle to effect some latching or locking action. Again, the fingers must be used to apply force close to, and in the direction of, the sharp part of the needle. If the plastic parts fail or distort, or if the users fingers slip, accidental contact with the needle is far too easy.
A pivoting needle sheath is disclosed by Luther U.S. Pat. No. 4,838,871, which is moved with the fingers toward the needle, again requiring placing the fingers in close proximity to the needle and moving them. See also Unger U.S. Pat. No. 4,872,552.
The present invention avoids having to ever place or move the user's finger near the sharp needle or scalpel blade by employing a self closing sheath that, once started, moves itself into position about the needle or blade.